To examine skin surface conditions, there have been known methods for analyzing horny cells. For example, McGinley reports a method therefor which comprises pressing a chamber onto the skin, dispersing horny cells in an aqueous solution of a nonionic surfactant, collecting the horny cells thus dispersed by centrifuging and then analyzing the conditions of the horny cells [Journal of Investigative Dermatology, Vol. 53, p. 107 (1969)].
Another method therefor comprises pressing the skin against the adhesive face of an adhesive tape, thus sampling horny cells onto the adhesive face, dissolving the horny cells in an organic solvent, collecting the horny cells by centrifuging, transferring the horny cells onto a slide glass and then analyzing the same. Alternatively, a slide glass coated with an adhesive is pressed onto the skin and thus the conditions of horny cells are analyzed [Shino, Journal of Society of Cosmetic Science, No. 2, 13 (1978)].
Furthermore, Kawai reports another method which comprises sampling horny cells from the skin with the use of an adhesive tape having a water-soluble adhesive, dispersing the horny cells together with the adhesive in a water-soluble solvent, filtering the dispersion through a membrane filter, transferring the horny cells, which have been optionally dispersed again, onto a slide glass, and then analyzing the conditions of the horny cells [Journal of Japanese Society of Dermatology), Vol. 99, No. 9, p. 999 (1989)].
In these methods, horny cells which have been preliminarily sampled are analyzed by dyeing followed by microscopic observation, counting a number of the cells, measuring the cell area, determining the ratio of nuclear cells, etc.
However, these conventional methods suffer from a problem that horny cells are damaged (i.e., suffering from the elimination of the constituents) due to the treatment with a solvent and thus cannot be properly analyzed. There is another problem that troublesome pretreatments including dyeing are required and thus horny cells cannot be quickly analyzed.
To overcome these problems, the present inventors have previously proposed a simplified method for counting cells which comprises pressing a transparent adhesive tape onto the skin, thus peeling off horny cells from the skin, irradiating the transparent adhesive tape having the horny cells adhering thereto with parallel beams, detecting the transmitted light, converting the transmitted light thus detected into a digital signal to thereby calculate the quantity of the transmitted light and counting the horny cells based on the relationship between the quantity of the transmitted light determined above and the cell count separately determined by the dyeing method (JP-A-7-55707; the term "JP-A" as used herein means an "unexamined published Japanese patent application"). By using this method, horny cells can be easily and quickly sampled and counted within a short period of time, thus evaluating the skin conditions.
The simplified method for counting cells disclosed in JP-A-7-55707 makes it possible to evaluate the skin conditions based on the count of the horny cells which have been peeled off from the skin and adhered to the transparent adhesive tape, namely, the skin conditions based on the peelability of the horny cells. However, it is impossible thereby to evaluate the skin conditions on the basis of the morphology, etc. of horny cells. Accordingly, the physiological conditions of the skin surface cannot be accurately evaluated by this method.